1. Field of the Invention
The present invention relates to a method for controlling a disk rotation speed within an optical disk apparatus for recording/reproducing information onto/from an optical information recording medium, and it relates, in particular, to an optical disk apparatus and a disk rotation speed control method thereof, for controlling the rotation speed of an optical disk by taking the mass eccentricity of the optical disk into the consideration thereof.
2. Description of the Related Arts
In an optical disk apparatus enabling to record/reproduce information onto/from an optical information recording medium, such as, an optical disk, for example, recording/reproducing of the information is made by irradiating a laser beam upon the information recording surface thereof, or detecting the reflection light thereon, while rotating the optical disk at high speed. On the optical disk to be rotated at the high speed within such the optical disk apparatus, the gravity position thereof sometimes comes off from a central position of rotation thereof, due to reasons, such as, adhesion of a label, or in the manufacturing process thereof, etc. (hereinafter, being called the “mass eccentricity”). When rotating such the optical disk having such the mass eccentricity at the high speed, the optical disk apparatus brings about vibration within an inner mechanism thereof, and accompanying with this, generating noises, and there is a possibility of failing to conduct a correct focus control. Further, there is also a possibility the optical disk is damaged or broken within the optical disk apparatus.
Conventionally, as a method for detecting such the mass eccentricity of the optical disk, in general, detection is made on the vibration generated accompanying with rotation of the disk. Also, conventionally, a lens error signal is detected as a signal indicative of a lens shift of a tracking actuator (hereinafter, being called a “lens shift indication signal”), or obtaining it from a tracking error signal, thereby detecting the mass eccentricity of the optical disk. However, in that instance, there is a problem that the tracking error signal leaks into the lens shift indication signal, such as, the lens error signal, etc., thereby erroneously detecting the mass eccentricity.
Then, as is known, in Japanese Patent Laying-Open No. 2005-92961 (2005) and Japanese Patent Laying-Open No. 2005-116042 (2005), for example, it is already to let the lens shift indication signal, such as, the lens error signal, etc., thereby preventing it from leaking into the lens error signal.